Foamed Cement Compositions Comprising Oil-Swellable Particles

ABSTRACT

Of the many compositions provided herein, an embodiment includes a foamed cement composition comprising a cementitious component, an oil-swellable particle comprising at least one swellable elastomer selected from the group consisting of acrylate butadiene rubber, polyacrylate rubber, isoprene rubber, choloroprene rubber, butyl rubber, brominated butyl rubber, chlorinated butyl rubber, chlorinated polyethylene, neoprene rubber, styrene butadiene block copolymer, sulphonated polyethylene, ethylene acrylate rubber, epichlorohydrin ethylene oxide copolymer, ethylene-propylene rubber, ethylene vinyl acetate copolymer, fluorosilicone rubber, silicone rubber, and combinations thereof, a foaming and stabilizing surfactant, gas, and water. Another embodiment includes a foamed cement composition comprising a cementitious component, an oil-swellable particle comprising a block copolymer of styrene butadiene rubber, a foaming and stabilizing surfactant, and gas.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 12/263,800, entitled “Foamed Cement Compositions ComprisingOil-Swellable Particles and Methods of Use,” filed on Nov. 3, 2008,which is a continuation-in-part of U.S. patent application Ser. No.12/283,398, filed on Sep. 11, 2008, entitled “Settable CompositionsComprising Cement Kiln Dust and Swellable Particles,” which is acontinuation-in-part of U.S. patent application Ser. No. 11/223,669,filed on Sep. 9, 2005, now U.S. Pat. No. 7,445,669, entitled “SettableCompositions Comprising Cement Kiln Dust and Additives(s).” U.S. patentapplication Ser. No. 12/263,800 is also a continuation-in-part of U.S.patent application Ser. No. 12/152,327, filed on May 14, 2008, entitled“Extended Cement Compositions Comprising Oil-Swellable Particles andAssociated Methods.” The disclosures of these related applications areincorporated herein by reference in their entirety.

BACKGROUND

The present invention relates to cementing operations, and moreparticularly in certain embodiments, to the application of anoil-swellable particle to foamed cement compositions, and methods ofusing such compositions in surface and subterranean applications.

Cement compositions are commonly utilized above ground (e.g., in theconstruction industry) and in subterranean operations, particularlysubterranean well completion and remedial operations. For example,cement compositions are used in primary cementing operations wherebypipe strings such as casings and liners may be cemented in well bores.In performing primary cementing, hydraulic cement compositions may bepumped into the annular space between the walls of a well bore and theexterior surface of the pipe string disposed therein. The cementcomposition is permitted to set in the annular space, thereby forming anannular sheath of hardened substantially impermeable cement therein thatsubstantially supports and positions the pipe string in the well boreand bonds the exterior surface of the pipe string to the walls of thewell bore. Cement compositions also may be used in remedial cementingoperations such as plugging highly permeable zones or fractures in wellbores, plugging cracks and holes in pipe strings, and the like.

Cement compositions utilized in subterranean operations may belightweight to prevent excessive hydrostatic pressure from being exertedon subterranean formations penetrated by the well bore, whereby theformations may be unintentionally fractured. One type of lightweightcement composition is a foamed cement composition, i.e., a cementcomposition that comprises a gas and a foaming surfactant. In additionto being lightweight, the gas contained in the foamed cement compositionmay improve the ability of the composition to maintain pressure andprevent the flow of formation fluids into and through the cementcomposition during its transition time, i.e., the time during which thecement composition changes from a true fluid to a set mass. Foamedcement compositions may be advantageous because they can have low fluidloss properties and may act to prevent the loss of fluid duringcirculation. Additionally, foamed cement compositions when set shouldhave a lower modulus of elasticity than non-foamed cements, which isoften desirable as it enables the resultant set cement, inter alia, toresist hoop stresses exerted on the set cement in the annulus.

Once set, the cement sheath may be subjected to a variety of cyclic,shear, tensile, impact, flexural, and/or compressive stresses that maylead to failure of the cement sheath. Such failure may be the result offractures, cracks, and/or debonding of the cement sheath from the pipestring and/or the formation. Undesirably, cement-sheath failure may leadto loss of zonal isolation, resulting, for example, in the undesirablemigration of fluids between formation zones. This may lead toundesirable consequences such as lost production, costly remedialoperations, environmental pollution, hazardous rig operations resultingfrom unexpected fluid flow from the formation caused by the loss ofzonal isolation, and/or hazardous production operations. Furthermore,failure of the cement sheath also may be caused by forces exerted byshifts in subterranean formations surrounding the well bore, cementerosion, and repeated impacts from the drill bit and the drill pipe.

SUMMARY

The present invention relates to cementing operations, and moreparticularly in certain embodiments, to the application of anoil-swellable particle to foamed cement compositions, and methods ofusing such compositions in surface and subterranean applications.

An embodiment of the present invention provides a method comprising:introducing a foamed cement composition into a subterranean formation,wherein the foamed cement composition comprises: a cementitiouscomponent; a foaming and stabilizing surfactant; an oil-swellableparticle; gas; and water; and allowing the settable composition to setin the subterranean formation.

Another embodiment of the present invention provides a methodcomprising: introducing a foamed cement composition into an annulusbetween a pipe string and a subterranean formation, wherein the foamedcement composition comprises comprising: a cementitious component; afoaming and stabilizing surfactant; an oil-swellable particle; gas; andwater; and allowing the settable composition to set in the annulus.

Another embodiment of the present invention provides a foamed cementcomposition comprising: a cementitious component, a foaming andstabilizing surfactant, a swellable particle, gas, and water.

The features and advantages of the present invention will be apparent tothose skilled in the art. While numerous changes may be made by thoseskilled in the art, such changes are within the spirit of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to cementing operations, and moreparticularly in certain embodiments, to the application of anoil-swellable particle to foamed cement compositions, and methods ofusing such compositions in surface and subterranean applications.

The foamed cement compositions of the present invention generallycomprise a cementitious component, water, a gas, a foaming andstabilizing surfactant, and an oil-swellable particle. As used herein,the term “cementitious component” refers to a material or combination ofmaterials that sets and hardens by reaction with water. The foamedcement compositions of the present invention should have a densitysuitable for a particular application as desired by those of ordinaryskill in the art, with the benefit of this disclosure. In someembodiments, the foamed settable compositions of the present inventionmay have a density in the range of from about 8 ppg to about 13 ppg.

Embodiments of the foamed cement compositions of the present inventioncomprise a cementitious component that may comprise cement kiln dust(“CKD.”) “CKD,” as that term is used herein, refers to a partiallycalcined kiln feed which may be removed from the gas stream andcollected in a dust collector during the manufacture of cement. CKDgenerally may comprise a variety of oxides, such as SiO₂, Al₂O₃, Fe₂O₃,CaO, MgO, SO₃, Na₂O, and K₂O. The CKD may be included in the foamedcement compositions in an amount sufficient to provide the desiredcompressive strength, density, and/or cost reduction. In someembodiments, the CKD may be present in the settable compositions of thepresent invention in an amount of at least about 25% by weight of thecementitious component. In some embodiments, the CKD may be present inthe settable compositions of the present invention in an amount in therange of from about 1% to about 75% by weight of the cementitiouscomponent. In some embodiments, the CKD may be present in the settablecompositions of the present invention in an amount in the range of fromabout 25% to about 50% by weight of the cementitious component.

Embodiments of the foamed cement compositions of the present inventionmay comprise a cementitious component that also comprises a hydrauliccement. In certain embodiments, the cementitious component may comprisehydraulic cement and CKD. A variety of hydraulic cements may be utilizedin accordance with the present invention, including, but not limited to,those comprising calcium, aluminum, silicon, oxygen, iron, and/orsulfur, which set and harden by reaction with water. Suitable hydrauliccements include, but are not limited to, Portland cements, pozzolanacements, gypsum cements, high alumina content cements, slag cements,silica cements, and combinations thereof. In certain embodiments, thehydraulic cement may comprise a Portland cement. In some embodiments,the Portland cements that are suited for use in the present inventioninclude those classified as Classes A through H according to AmericanPetroleum Institute, API Specification for Materials and Testing forWell Cements, API Specification 10, Fifth Ed., Jul. 1, 1990. In certainembodiments, API Class A, C, G and H hydraulic cements may be preferred.

Where present, the hydraulic cement generally may be included in thecement compositions in an amount sufficient to provide the desiredcompressive strength, density, and/or cost. In some embodiments, thehydraulic cement may be present in the cement compositions of thepresent invention in an amount of about 0.1% to about 100% by weight ofcementitious materials. In some embodiments, the hydraulic cement may bepresent in the cement compositions of the present invention in an amountof about 0.1% to about 95% by weight of cementitious materials. In someembodiments, the hydraulic cement may be present in the cementcompositions of the present invention in an amount of about 20% to about95% by weight by weight of cementitious materials. In some embodiments,the hydraulic cement may be present in the cement compositions of thepresent invention in an amount in the range of from about 50% to about90% by weight of cementitious materials.

In some embodiments, a pozzolana cement that may be suitable for usecomprises fly ash. As used herein, “fly ash” refers to the residue fromthe combustion of powdered or ground coal, wherein the fly ash carriedby flue gases may be recovered, for example, by electrostaticprecipitation. A variety of fly ashes may be suitable, including fly ashclassified as Class C and Class F fly ash according to AmericanPetroleum Institute, API Specification for Materials and Testing forWell Cements, API Specification 10, Fifth Ed., Jul. 1, 1990. Class C flyash comprises both silica and lime so that, when mixed with water, itsets to form a hardened mass. Class F fly ash generally does not containsufficient lime, so an additional source of calcium ions is required forthe Class F fly ash to form a cement composition with water. In someembodiments, lime may be mixed with Class F fly ash in an amount in therange of from about 0.1% to about 25% by weight of the fly ash. In someinstances, the lime may be hydrated lime. Suitable examples of fly ashinclude, but are not limited to, “POZMIX® A” cement additive,commercially available from Halliburton Energy Services, Inc., Duncan,Okla.

Where present, the fly ash generally may be included in the cementcompositions in an amount sufficient to provide the desired compressivestrength, density, and/or cost. In some embodiments, the fly ash may bepresent in the cement compositions of the present invention in an amountof about 5% to about 75% by weight of cementitious materials. In someembodiments, the fly ash may be present in the cement compositions ofthe present invention in an amount of about 5% to about 50% by weight ofcementitious materials.

In some embodiments, a slag cement that may be suitable for use maycomprise slag. As used herein, “slag” refers to a granulated, blastfurnace by-product formed in the production of cast iron and generallycomprises oxidized impurities found in iron ore. Slag generally does notcontain sufficient basic material, so slag cement further may comprise abase to produce a cement composition that may react with water to set toform a hardened mass. Examples of suitable sources of bases include, butare not limited to, sodium hydroxide, sodium bicarbonate, sodiumcarbonate, lime, and combinations thereof.

Where present, the slag cement generally may be included in the cementcompositions in an amount sufficient to provide the desired compressivestrength, density, and/or cost. In some embodiments, the slag cement maybe present in the cement compositions of the present invention in anamount of 0% to about 75% by weight of cementitious materials. In someembodiments, the slag cement may be present in the cement compositionsof the present invention in an amount of about 5% to about 40% by weightof cementitious materials.

The water used in the foamed cement compositions of the presentinvention may be freshwater, saltwater (e.g., water containing one ormore salts dissolved therein), brine (e.g., saturated saltwater producedfrom subterranean formations), or seawater, or combinations thereof.Generally, the water may be from any source, provided that it does notcontain an excess of compounds that may adversely affect othercomponents in the cement composition. The water may be present in anamount sufficient to form a pumpable slurry. More particularly, thewater may be present in an amount in the range of from about 33% andabout 200% by weight of the cementitious materials. In some embodiments,the water may be present in an amount in the range of from about 35% andabout 70% by weight of cementitious materials.

The gas utilized in the foamed cement compositions of the presentinvention may be any gas suitable for foaming a cement composition,including, but not limited to, air or nitrogen, or combinations thereof.Generally, the gas should be present in the foamed cement compositionsof the present invention in an amount sufficient to form a suitablefoam. In certain embodiments, the gas may be present in an amount in therange of from about 10% and about 80% by volume of the composition.

Any suitable foaming and stabilizing surfactant may be used in thefoamed cement composition of the present invention. Among other things,the foaming and stabilizing surfactants may facilitate the foaming of acement composition and/or also stabilize the resultant foamed cementcomposition formed therewith. Suitable foaming and stabilizingsurfactants may include, but are not limited to: mixtures of an ammoniumsalt of an alkyl ether sulfate, a cocoamidopropyl betaine surfactant, acocoamidopropyl dimethylamine oxide surfactant, sodium chloride, andwater; mixtures of an ammonium salt of an alkyl ether sulfatesurfactant, a cocoamidopropyl hydroxysultaine surfactant, acocoamidopropyl dimethylamine oxide surfactant, sodium chloride, andwater; hydrolyzed keratin; mixtures of an ethoxylated alcohol ethersulfate surfactant, an alkyl or alkene amidopropyl betaine surfactant,and an alkyl or alkene dimethylamine oxide surfactant; aqueous solutionsof an alpha-olefinic sulfonate surfactant and a betaine surfactant; andcombinations thereof. An example of a suitable hydrolyzed keratin isdescribed in U.S. Pat. No. 6,547,871, the disclosure of which isincorporated herein by reference. Example of suitable mixtures of anethoxylated alcohol ether sulfate surfactant, an alkyl or alkeneamidopropyl betaine surfactant, and an alkyl or alkene dimethylamineoxide surfactant is described in U.S. Pat. No. 6,063,738, the disclosureof which is incorporated herein by reference. Examples of suitableaqueous solutions of an alpha-olefinic sulfonate surfactant and abetaine surfactant are described in U.S. Pat. No. 5,897,699, thedisclosure of which is incorporated herein by reference. In oneembodiment, the foaming and stabilizing surfactant comprises a mixtureof an ammonium salt of an alkyl ether sulfate, a cocoamidopropyl betainesurfactant, a cocoamidopropyl dimethylamine oxide surfactant, sodiumchloride, and water.

Generally, the foaming and stabilizing surfactants should be present inthe foamed cement compositions of the present invention in an amountsufficient to provide a suitable foam. In some embodiments, the foamingand stabilizing surfactant may be present in an amount in the range offrom about 0.8% and about 5% by volume of the water (“bvow”) present inthe foamed cement composition.

Embodiments of the foamed cement compositions may comprise anoil-swellable particle. As used herein, a particle is characterized asoil-swellable when it swells upon contact with oil. Oil-swellableparticles suitable for use in embodiments of the present invention maygenerally swell by up to about 50% of their original size at thesurface. Under downhole conditions, this swelling may be more, or less,depending on the conditions presented. For example, the swelling may beat least 10% at downhole conditions. In some embodiments, the swellingmay be up to about 50% under downhole conditions. However, as those ofordinary skill in the art, with the benefit of this disclosure, willappreciate, the actual swelling when the oil-swellable particles areincluded in a foamed cement composition may depend on, for example, theconcentration of the swellable particles included in the settablecomposition. In accordance with embodiments of the present invention,the swellable particles may be included in the settable composition, forexample, to counteract the formation of cracks in the cement sheathand/or micro-annulus between the cement sheath and the pipe string orthe formation. In general, the oil-swellable particles should be capableof swelling when contacted by oil to inhibit fluid flow through thecrack and/or micro-annulus. Accordingly, the oil-swellable particles mayprevent and/or reduce the loss of zonal isolation in spite of theformation of cracks and/or micro-annulus, potentially resulting in animproved annular seal for the foamed cement compositions.

An example of an oil-swellable particle that may be utilized inembodiments of the present invention comprises an oil-swellableelastomer. Oil-swellable elastomers suitable for use in embodiments ofthe present invention may generally swell by up to about 100% of theiroriginal size at the surface when contacted by oil. Under downholeconditions, this swelling may be more, or less, depending on theconditions presented. For example, the swelling may be at least 10% atdownhole conditions. In some embodiments, the swelling may be up toabout 50% under downhole conditions. However, as those of ordinary skillin the art, with the benefit of this disclosure, will appreciate, theactual swelling when the swellable elastomer is included in a foamedcement composition may depend on, for example, the concentration of theoil-swellable elastomer included in the foamed cement composition,downhole pressure, and downhole temperature, among other factors. Somespecific examples of suitable swellable elastomers include, but are notlimited to, natural rubber, acrylate butadiene rubber, polyacrylaterubber, isoprene rubber, choloroprene rubber, butyl rubber (IIR),brominated butyl rubber (BIIR), chlorinated butyl rubber (CIIR),chlorinated polyethylene (CM/CPE), neoprene rubber (CR), styrenebutadiene copolymer rubber (SBR), styrene butadiene block copolymerrubber, sulphonated polyethylene (CSM), ethylene acrylate rubber(EAM/AEM), epichlorohydrin ethylene oxide copolymer (CO, ECO),ethylene-propylene rubber (EPM and EDPM), ethylene-propylene-dieneterpolymer rubber (EPT), ethylene vinyl acetate copolymer,fluorosilicone rubbers (FVMQ), silicone rubbers (VMQ), poly2,2,1-bicyclo heptene (polynorborneane), alkylstyrene, and crosslinkedvinyl acrylate copolymers. Combinations of suitable oil-swellableelastomers may also be utilized. One example of a suitable oil-swellableelastomer comprises a block copolymer of a styrene butadiene rubber.Other swellable elastomers that behave in a similar fashion with respectto oil also may be suitable. Those of ordinary skill in the art, withthe benefit of this disclosure, will be able to select an appropriateoil-swellable elastomer for use in the compositions of the presentinvention based on a variety of factors, including the application inwhich the composition will be used and the desired oil-swellablecharacteristics.

Where used, the oil-swellable particle generally may be included in thecement compositions in an amount sufficient to provide the desiredmechanical properties. In some embodiments, the oil-swellable particlemay be present in the foamed cement compositions in an amount up toabout 27% bwoc (e.g., about 1%, about 5%, about 10%, about 15%, about20%, about 25%, etc.), alternatively in a range of about 1% to about 25%bwoc, and alternatively in a range of about 4% to about 20% bwoc.

In addition, the oil-swellable particle that is utilized may have a widevariety of shapes and sizes of individual particles suitable for use inaccordance with embodiments of the present invention. By way of example,the oil-swellable particle may have a well-defined physical shape aswell as an irregular geometry, including the physical shape ofplatelets, shavings, fibers, flakes, ribbons, rods, strips, spheroids,beads, toroids, pellets, tablets, or any other physical shape. In someembodiments, the oil-swellable particle may have a particle size in therange of about 5 microns to about 1,500 microns. In some embodiments,the oil-swellable particle may have a particle size in the range ofabout 20 microns to about 500 microns. However, particle sizes outsidethese defined ranges also may be suitable for particular applications.Particle sizes may be measured using a laser light scattering particlesize analyzer from the Malvern Company.

In certain embodiments, the settable compositions of the presentinvention further may comprise metakaolin. Generally, metakaolin is awhite pozzolan that may be prepared by heating kaolin clay, for example,to temperatures in the range of from about 600° to about 800° C. In someembodiments, the metakaolin may be present in the settable compositionsof the present invention in an amount in the range of from about 1% toabout 50% by weight. In some embodiments, the metakaolin may be presentin an amount in the range of from about 10% to about 50% by weight.

In certain embodiments, the settable compositions of the presentinvention further may comprise shale. Among other things, shale includedin the settable compositions may react with excess lime to form asuitable cementing material, for example, calcium silicate hydrate. Avariety of shales are suitable, including those comprising silicon,aluminum, calcium, and/or magnesium. An example of a suitable shalecomprises vitrified shale. Suitable examples of vitrified shale include,but are not limited to, “PRESSUR-SEAL® FINE LCM” material and“PRESSUR-SEAL® COARSE LCM” material, which are commercially availablefrom TXI Energy Services, Inc., Houston, Tex. Generally, the shale mayhave any particle size distribution as desired for a particularapplication. In certain embodiments, the shale may have a particle sizedistribution in the range of from about 37 micrometers to about 4,750micrometers.

Where present, the shale may be included in the settable compositions ofthe present invention in an amount sufficient to provide the desiredcompressive strength, density, and/or cost. In some embodiments, theshale may be present in an amount in the range of from about 1% to about75% by weight. In some embodiments, the shale may be present in anamount in the range of from about 5% to about 35% by weight. One ofordinary skill in the art, with the benefit of this disclosure, willrecognize the appropriate amount of the shale to include for a chosenapplication.

In certain embodiments, the settable compositions of the presentinvention further may comprise zeolite. Zeolites generally are porousalumino-silicate minerals that may be either a natural or syntheticmaterial. Synthetic zeolites are based on the same type of structuralcell as natural zeolites, and may comprise aluminosilicate hydrates. Asused herein, the term “zeolite” refers to all natural and syntheticforms of zeolite.

In certain embodiments, suitable zeolites for use in present inventionmay include “analcime” (which is hydrated sodium aluminum silicate),“bikitaite” (which is lithium aluminum silicate), “brewsterite” (whichis hydrated strontium barium calcium aluminum silicate), “chabazite”(which is hydrated calcium aluminum silicate), “clinoptilolite” (whichis hydrated sodium aluminum silicate), “faujasite” (which is hydratedsodium potassium calcium magnesium aluminum silicate), “ferrierite”,“harmotome” (which is hydrated barium aluminum silicate), “heulandite”(which is hydrated sodium calcium aluminum silicate), “laumontite”(which is hydrated calcium aluminum silicate), “mesolite” (which ishydrated sodium calcium aluminum silicate), “natrolite” (which ishydrated sodium aluminum silicate), “paulingite” (which is hydratedpotassium sodium calcium barium aluminum silicate), “phillipsite” (whichis hydrated potassium sodium calcium aluminum silicate), “scolecite”(which is hydrated calcium aluminum silicate), “stellerite” (which ishydrated calcium aluminum silicate), “stilbite” (which is hydratedsodium calcium aluminum silicate), and “thomsonite” (which is hydratedsodium calcium aluminum silicate), and combinations thereof. In certainembodiments, suitable zeolites for use in the present invention includechabazite and clinoptilolite. An example of a suitable source of zeoliteis available from the C2C Zeolite Corporation of Calgary, Canada.

In some embodiments, the zeolite may be present in the settablecompositions of the present invention in an amount in the range of fromabout 1% to about 40% by weight. In certain embodiments, the zeolite maybe present in an amount in the range of from about 5% to about 25% byweight.

In certain embodiments, the settable compositions of the presentinvention further may comprise a set retarding additive. As used herein,the term “set retarding additive” refers to an additive that retards thesetting of the settable compositions of the present invention. Examplesof suitable set retarding additives include, but are not limited to,ammonium, alkali metals, alkaline earth metals, metal salts ofsulfoalkylated lignins, hydroxycarboxy acids, copolymers that compriseacrylic acid or maleic anhydride, and combinations thereof. One exampleof a suitable sulfoalkylate lignin comprises a sulfomethylated lignin.Suitable set retarding additives are disclosed in more detail in U.S.Pat. No. Re. 31,190, the entire disclosure of which is incorporatedherein by reference. Suitable set retarding additives are commerciallyavailable from Halliburton Energy Services, Inc. under the tradenames“HR® 4,” “HR® 5,” HR® 7,” “HR® 12,” “HR® 15,” HR® 25,” “SCR™ 100,” and“SCR™ 500.” Generally, where used, the set retarding additive may beincluded in the settable compositions of the present invention in anamount sufficient to provide the desired set retardation. In someembodiments, the set retarding additive may be present in an amount inthe range of from about 0.1% to about 5% by weight.

Optionally, other additional additives may be added to the settablecompositions of the present invention as deemed appropriate by oneskilled in the art, with the benefit of this disclosure. Examples ofsuch additives include, but are not limited to, accelerators, weightreducing additives, heavyweight additives, lost circulation materials,filtration control additives, dispersants, and combinations thereof.Suitable examples of these additives include crystalline silicacompounds, amorphous silica, salts, fibers, hydratable clays,microspheres, pozzolan lime, latex cement, thixotropic additives,combinations thereof and the like.

The foamed cement compositions of the present invention may be preparedin accordance with any suitable technique. For example, the cementitiouscomponent and water may be combined and mixed for a sufficient period oftime to form a pumpable cement composition. Liquid additives, if any,may be mixed with the water prior to combination with the cementitiouscomponent. Dry solid additives, if any, may be dry blended with thecement prior to combination with the water. In certain embodiments, thecement composition then may be pumped to the well bore, and the foamingand stabilizing surfactant followed by the gas may be injected into thecement composition, e.g., at a foaming mixing “T,” as the cementcomposition is being pumped, in an amount sufficient to form a foamedcement composition. After foaming, the foamed cement composition, may beplaced in a desired location within the well bore and allowed to set.Those of ordinary skill in the art, with the benefit of this disclosure,will recognize other suitable techniques for preparing the foamed cementcompositions of the present invention.

An example of a method of cementing of the present invention comprises:placing a foamed cement composition in a location to be cemented,wherein the foamed cement composition comprises a cementitious componentcomprising a hydraulic cement and CKD, water, a foaming and stabilizingsurfactant, and an oil-swellable particle; and allowing the foamedcement composition to set. The location to be cemented may be anysuitable location, including a location above ground or a portion of asubterranean formation, such as between the walls of a well bore and theexterior surface of a pipe string disposed therein.

Another example of a method of cementing of the present inventioncomprises: providing a cement composition that comprises a cementitiouscomponent comprising a hydraulic cement and CKD, water, a foaming andstabilizing surfactant, and an oil-swellable particle; combining thecement composition with a gas to form a foamed cement composition;placing the foamed cement composition in a portion of a subterraneanformation; and allowing the foamed cement composition to set therein.

To facilitate a better understanding of the present invention, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, thescope of the invention.

Example 1

A 14 lb/gal Portland class H cement slurry was prepared. The slurrycontained 5% amorphous silica (by weight of cement) and 20%oil-swellable elastomer (by weight of cement). The oil-swellable rubberwas a block polymer of styrene-butadiene. The slurry was foamed down to11 lb/gal using 2% foamer 760 by volume of water. Foam weight reachedthe desired level by mixing in a pressurized foam blending jar for fiveseconds. For comparison purposes, a slurry was also prepared without theoil-swellable elastomer. The foamed slurries were cured at 140° F. for24 hours. Physical and mechanical properties are reported in Table 1.Compressive strength testing was performed in accordance with APIRecommended Practices 10B, Twenty-Second Edition, December 1997. TheYoung's Modulus of Elasticity and the Poisson's Ratio were determined inaccordance with ASTM D3148-02.

TABLE I Premium cement mixed at 14 lbs/gal, with 2% bvow foamerOil-Swellable 24-hr Strength, Young's Poisson's Sample Elastomer, % bwocPSI Modulus Ratio No. 1 — 801 2.75E+05 0.1575 No. 2 20 1060 3.53E+050.184

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Whilenumerous changes may be made by those skilled in the art, such changesare encompassed within the spirit of this invention as defined by theappended claims. The terms in the claims have their plain, ordinarymeaning unless otherwise explicitly and clearly defined by the patentee.

1. A foamed cement composition comprising: a cementitious component, anoil-swellable particle comprising at least one swellable elastomerselected from the group consisting of acrylate butadiene rubber,polyacrylate rubber, isoprene rubber, choloroprene rubber, butyl rubber,brominated butyl rubber, chlorinated butyl rubber, chlorinatedpolyethylene, neoprene rubber, styrene butadiene block copolymer,sulphonated polyethylene, ethylene acrylate rubber, epichlorohydrinethylene oxide copolymer, ethylene-propylene rubber, ethylene vinylacetate copolymer, fluorosilicone rubber, silicone rubber, andcombinations thereof, a foaming and stabilizing surfactant, gas, andwater.
 2. The foamed cement composition of claim 1 wherein thecementitious component comprises cement kiln dust.
 3. The foamed cementcomposition of claim 1 wherein the cementitious component compriseshydraulic cement.
 4. The foamed cement composition of claim 1 whereinthe cementitious component comprises cement kiln dust in an amount ofabout 1% to about 75% by weight of the cementitious component.
 5. Thefoamed cement composition of claim 1 wherein the oil-swellable particleis present in the foamed cement composition in an amount of about 1% toabout 27% by weight of the cementitious component.
 6. The foamed cementcomposition of claim 1 wherein the oil-swellable particle is capable ofswelling by at least 10% at downhole conditions.
 7. The foamed cementcomposition of claim 1 wherein the foaming and stabilizing surfactantcomprises at least one surfactant selected from the group consisting of:a mixture of an ammonium salt of an alkyl ether sulfate, acocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamineoxide surfactant, sodium chloride, and water; a mixture of an ammoniumsalt of an alkyl ether sulfate surfactant, a cocoamidopropylhydroxysultaine surfactant, a cocoamidopropyl dimethylamine oxidesurfactant, sodium chloride, and water; a hydrolyzed keratin; a mixtureof an ethoxylated alcohol ether sulfate surfactant, an alkyl or alkeneamidopropyl betaine surfactant, and an alkyl or alkene dimethylamineoxide surfactant; an aqueous solution of an alpha-olefinic sulfonatesurfactant and a betaine surfactant; and combinations thereof.
 8. Thefoamed cement composition of claim 1 wherein the foamed cementcomposition comprises at least one additive selected from the groupconsisting of fly ash, slag, metakaolin, shale, zeolite, a crystallinesilica compound, amorphous silica, salt, fiber, hydratable clay, amicrosphere, pozzolan lime, latex cement, a thixotropic additive, andcombinations thereof.
 9. The foamed cement composition of claim 1wherein the foamed cement composition comprises at least one additiveselected from the group consisting of a set retarding additive, anaccelerator, a weight reducing additive, a heavyweight additive, a lostcirculation material, a filtration control additive, a dispersant, andcombinations thereof.
 10. The foamed cement composition of claim 1wherein the foamed cement composition has a density of about 8 poundsper gallon to about 13 pounds per gallon, and wherein the gas is presentin an amount of about 10% to about 80% by volume of the foamed cementcomposition.
 11. A foamed cement composition comprising: a cementitiouscomponent, an oil-swellable particle comprising a block copolymer ofstyrene butadiene rubber, a foaming and stabilizing surfactant, and gas.12. The foamed cement composition of claim 11 wherein the cementitiouscomponent comprises cement kiln dust.
 13. The foamed cement compositionof claim 11 wherein the cementitious component comprises hydrauliccement.
 14. The foamed cement composition of claim 11 wherein thecementitious component comprises cement kiln dust in an amount of about1% to about 75% by weight of the cementitious component.
 15. The foamedcement composition of claim 11 wherein the oil-swellable particle ispresent in the foamed cement composition in an amount of about 1% toabout 27% by weight of the cementitious component.
 16. The foamed cementcomposition of claim 11 wherein the oil-swellable particle is capable ofswelling by at least 10% at downhole conditions.
 17. The foamed cementcomposition of claim 11 wherein the foaming and stabilizing surfactantcomprises at least one surfactant selected from the group consisting of:a mixture of an ammonium salt of an alkyl ether sulfate, acocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamineoxide surfactant, sodium chloride, and water; a mixture of an ammoniumsalt of an alkyl ether sulfate surfactant, a cocoamidopropylhydroxysultaine surfactant, a cocoamidopropyl dimethylamine oxidesurfactant, sodium chloride, and water; a hydrolyzed keratin; a mixtureof an ethoxylated alcohol ether sulfate surfactant, an alkyl or alkeneamidopropyl betaine surfactant, and an alkyl or alkene dimethylamineoxide surfactant; an aqueous solution of an alpha-olefinic sulfonatesurfactant and a betaine surfactant; and combinations thereof.
 18. Thefoamed cement composition of claim 11 wherein the foamed cementcomposition comprises at least one additive selected from the groupconsisting of fly ash, slag, metakaolin, shale, zeolite, a crystallinesilica compound, amorphous silica, salt, fiber, hydratable clay, amicrosphere, pozzolan lime, latex cement, a thixotropic additive, andcombinations thereof.
 19. The foamed cement composition of claim 11wherein the foamed cement composition comprises at least one additiveselected from the group consisting of a set retarding additive, anaccelerator, a weight reducing additive, a heavyweight additive, a lostcirculation material, a filtration control additive, a dispersant, andcombinations thereof.
 20. The foamed cement composition of claim 11wherein the foamed cement composition has a density of about 8 poundsper gallon to about 13 pounds per gallon, and wherein the gas is presentin an amount of about 10% to about 80% by volume of the foamed cementcomposition.